I do multiple short etches (5 mins ish), scrubbed with a pan scourer and dish soap in between (like my american lingo ? ) When you can just about feel a bit of topography stop and clean it up. You can always etch more after if you dont like the effect.
Im not into this 'setting the oxides' thing, I like to know all scuz has gone from the blade as I mostly do chefs knives. I sand with 1000g wet and dry on a hard backing to hit the high spots, and thats what makes it pop. Also hit it with some flitz or metal polish, on a piece of leather glued to a hard backing.
One observation I have is that blades look different 'in the hand' to the photographs people post on line. In my experience, sometimes the shiny Ni. layers look like the 'black' layers in a photo as they are reflecting something dark. The one below in the photo looks way more contrasted in the pics than it does in the hand. (the photo is straight from my phone, no editing)